1. Field of the Invention
The invention relates to footwear and, particularly, footwear for any of various sports and/or for hiking. More particularly, footwear of the invention include those having a double upper, in the sense that the upper includes an outer envelope and an inner envelope. Footwear of this type can include athletic footwear for use in fields such as hiking, racing on flat or mountainous terrain, skateboarding, ball-playing sports, cross-country or telemark skiing, snowboarding, snowshoeing, and the like.
2. Background Information
For the intended use, each article of footwear, i.e., each boot or shoe (hereafter, “shoe” for convenience), must have a certain flexibility and a good damping capability. Flexibility must be understood as the ability to closely follow certain deformations of the foot. This involves, for example, enabling good foot rolling movement when walking. Damping serves to reduce, or even prevent, fatigue or injuries that can result from supports or impacts on the ground, or from various forces.
A shoe must also fulfill a variety of functions, sometimes contradictory, such as ensuring adequate support and/or tightening of the foot, while also providing it with satisfactory comfort.
Thus, it is known to manufacture shoes as shown in FIGS. 1 and 2. These two figures illustrate, in total and partial transverse cross section, respectively, an outer sole assembly 2 and an upper 3. The upper includes a first envelope 4 and a second envelope 5, both being adapted to cover the foot directly or indirectly. The first envelope 4 is associated with a first lasting sole 6 to form a first fitting element 7. The second envelope 5 is associated with a second lasting sole 8 to form a second fitting element 9, the latter being mounted inside the first fitting element 7. The second fitting element 9 is typically a slipper, i.e., a liner. Consequently, the lasting soles 6, 8 are part of an inner sole assembly 10. The first envelope 4 of the shoe 1 extends in the area of a lateral side 11 and a medial side 12, as well as in the area of a substantial portion of the first lasting sole 6. This structure is conventional, because the first envelope 4 is mounted upon the lasting sole 6 by means of an adhesive, or cement, layer 13. The sole 6 is relatively rigid in order to withstand the assembly process, also referred to as the lasting process. The adhesive process is carried by pulling the envelope 4 so as to press it flat upon the sole 6, a last being inserted in the fitting element 7. This is referred to as the conventional lasting. This makes it possible to exert sufficient pressure while the adhesive is being heated in order to obtain the first fitting element 7. The second fitting element 9 is obtained, for example, by affixing the second envelope 5 to the second lasting sole 8 using stitching 14. This is referred to as strobel lasting. The sole 8, which is flexible and can be stitched, is called the strobel sole. Alternatively, a molded, unitary structure, or any equivalent, could be provided.
It is to be understood that the first fitting element 7 is adapted to ensure support and tightening of the foot, while the second fitting element 9 fulfills other functions, such as providing a certain comfort. In addition, the first fitting element 7 is affixed to the outer sole assembly 2 via an adhesive layer 15. In the end, the shoe 1 according to FIGS. 1 and 2 has a certain flexibility and a certain damping capability.
Generally speaking, flexible shoes provided with two fitting elements according to the prior art have the following disadvantage: they still hinder the foot rolling movement, at least partially, due to the rigid lasting board, especially for racing; and the transmission of supports, impacts, and other forces is overly intense. In other words, known shoes lack flexibility, and their damping capability is insufficient, because the folded portion of the envelope 4, associated with the adhesive layer 13, creates an extra thickness that increases the rigidity of the shoe.
Another disadvantage is that of thermal insulation. Indeed, under difficult conditions of use, such as walking in snow, the user's feet can become cold. This is due to the formation of a thermal bridge at the junction between the upper and the outer sole assembly, such bridge being created by the crushing of the material during the conventional lasting operation. Indeed, during this operation, it is necessary to heat and pull very hard on the constituent materials of the envelope 4.
Another disadvantage is that of the conventional lasting, rendering the manufacturing process difficult. Indeed, adhesively positioning of an envelope on a lasting sole is a relatively difficult process. Powerful and precise machines are necessary for pulling, positioning, and gluing the envelope.
Another disadvantage inherent in certain known flexible shoes, is the poor positional stability of the second fitting element in the first. For example, removing the foot sometimes causes an undesired displacement of the second element with respect to the first.